Core compositions for solid golf balls primarily contain cross-linked polybutadiene. The polybutadiene is typically mixed with other materials to obtain a uniform composition. This composition is formed into the spherical cores of the golf balls using either an injection mold or a compression mold.
In the case of compression molding, the uniform composition is fed into a screw-type extruder that forces the composition through a die. The composition exits the die as a continuous length or extrudate at a predetermined discharge rate. The extrudate is guided past a cutting device, for example a rotating knife having a substantially constant cutting rate, and is cut into discrete pieces called preforms. Each preform is advanced to a spherical cavity defined by a pair of half-molds within the compression mold. The compression mold subjects the preform to heat and pressure, which causes the preform to expand and fill the spherical cavity. The preform is cured by heat in the mold to form a golf ball core. For injection molding, the core composition is injected directly into the spherical cavities of the mold.
A typical mold does not contain a single spherical cavity but a plurality of cavities arranged in columns and rows, i.e., a matrix. In order to maintain the matrix in continuous sheet form, cavities are filled with an excess of rubber stock required to completely fill the cavities and the excess rubber spills out of the cavity as “overflow.” The overflow from individual cavities knits together with overflows from adjacent cavities to form the matrix sheet with molded parts fixed within the sheet. After all of the cavities within the mold are filled with rubber stock and the formed spherical cores are connected to the sheet in a suspended manner through webs or runners. Individual cores are separated from the matrix. Portions of the overflow remain attached to the separated cores and can cause equipment malfunction in subsequent manufacturing processes.
Current rubber molding technology includes items such as parts die-out devices at the molding press to separate individual cores from the matrix. Subsequent processing of the cores into finished golf balls requires cooling of the cores and manual handling. However, cooling adds significant time to the process and manual handling also adds time and associated costs. Attempts at decreasing the cooling time by immediately quenching the cores can reduce the desirable cross-linking in the core that can adversely affect the physical properties of the core.
Therefore, there remains a need for a system for molding golf ball cores that reduces the cooling time of the cores after molding but does not adversely affect the physical properties of the core. In addition, the system should be sufficiently automated optionally with a device to sort out cores with molding flash attached so as to minimize the need for significant manual handling of the golf ball cores.